Sea's Lost Daughter
by Nightingale0708
Summary: Percy, Annabeth, Thalia and Grover wake up in Camp Half-Blood thinking it's a normal day. Well it's not. A girl around their age stumbles in the boundaries after fighting off several battalions of hellhounds. The girl is amazing at everything but is able to control water, so she is claimed as a daughter of Poseidon. Full summary inside. Rated M for language.
1. Chapter 1

^^OOo(With Percy)oOO^^

Percy woke up after a relatively peaceful sleep, which was unusual. He sat up and rubbed his eyes, looking around his cabin. The decorations Tyson had put up were still there and Cabin 3 was still spotless from his stay. Percy's shield had been fixed and he'd even made Annabeth a few throwing knives, which she'd accepted slightly awkwardly. Percy and Grover had gotten punched later on because they were laughing at the look on her face. His arm still hurt.

Percy got up and pulled on some pants and his Camp Half-Blood shirt. He always slept with his beaded necklace, so he didn't need to put that on. He took his shield/ watch from his nightstand and put it on. He ran a hand through his lengthy jet black hair. There was no chance at trying to tame it, he'd tried a billion times already. His sea green eyes looked out the window facing the sea. Percy walked over to it and leaned against the railing, taking a deep breath of the salty sea air. But that did nothing to tame the feeling of foreboding growing in his stomach. Something was goin to happen, something big. He just didn't know what.

Percy shook his head, trying to clear it. He couldn't think that way. Today was Friday and Percy was pumped. He'd already paired up with Cabin 1, 6, 7, 11 and 12. That's Zeus, Poseidon, Athena, Apollo, and Hermes. Clarisse represented Cabin 5 and she paired up with Cabin 4, 9, and 10. That's Demeter, Ares, Hephaestus, and Aphrodite. The only ones who actually knew how to swing a sword was 5 and 9, so Percy wasn't that worried. But there was a lot in 5 and a lot in 9, so they could be overrun. But not without a fight.

Percy walked out of his cabin to find that the Apollo kids were already playing basketball. Percy scanned the torrents of teenagers, searching for a certain daughter of Athena. He finally found her, leaning against a tree talking to Grover. He started walking over to them. Annabeth noticed his approach and turned to him, her stormy gray eyes bright with excitement. She waved.

Percy finally reached his friends, his hands in his pockets.

"So, are you excited?" Annabeth immediately asked.

"I'm always excited to kick some Ares butt but yes. Yes I am." he responded. Grover chuckled.

"Well, for once, I'm bummed that I can't take part in these activities because this is gonna be the fight of the century."

"Don't worry, Grover. I'm sure you'll find something to do." A voice said. We turned to the side to see our friend, Thalia, daughter of Zeus. She's in one of the cabins we partnered with. Suddenly, the conch shell blew, signaling the start of breakfast.

"Great. I'm starving." Percy said, almost sprinting to the mess hall. Annabeth groaned and followed him, Grover and Thalia following suit. They were one of the first ones to arrive. Percy whooped and hurried over to his table. Thalia followed him, mumbling something about him always making a scene. They sat down together at Poseison's table and were immediately served their breakfast. Annabeth left to go find her own cabin mates while Grover joined Thalia and Percy.

They finished breakfast within an hour and walked out of the mess hall, now at a loss of what to do.

"Well, what now?" Grover asked.

"Wanna spar, Jackson?" Thalia said, elbowing him in the ribs while grinning mischievously.

Percy smiled. "You're on!" he yelled, taking off running.

"Hey!" Thalia yelled as she had to sprint to catch up. Annabeth and Grover looked at each other and groaned at the thought of running after breakfast.

"Wanna just walk?" Grover asked.

"Sure." Annabeth replied.

Meanwhile, Thalia and Percy had already reached the arena. They walked to the center of the room and took out heir weapons, which didn't really look like much. Percy was holding a ballpoint pen and Thalia was holding a golden coin in her hand. Suddenly, Percy uncapped his pen and the pen transformed into a brilliant bronze sword. He charged at Thalia, who flipped her coin up in the air. The coin transformed into a spear, which she leveled at Percy's chest. The two sparred for a few moments, parrying, swinging and ducking out of the way of each other's strikes.

Suddenly, Thalia slapped a bracelet she had in her left arm, expanding it into a full size sheild. Percy laughed.

"Two can play at that game, princess." He said, pressing the button on the side of his watch. Thalia watched in awe as it expanded into a leather strap shield.

"What's wrong, princess? Afraid of the competition?" He teased, annoying her to no end. They continued sparing until Annabeth and Grover got there. Grover sat and watched as the three demigods sparred until conch shell blew again for lunch. After they ate, they played several games of volleyball with the Apollo and Hephaestus kids. The sun was beginning to set as the conch horn blew for dinner. Again they ate, filling up on healthy food for the upcoming battle. Then, they made their way to the edge of the forest, battle ready. There, they discussed their battle plan.

Annabeth and Will Solace from Apollo would be guarding the perimeter of the flag while Thalia and Percy led a head on attack to get the other teams flag, consisting of most of the Athena and Hermes cabins. The kids from 12 and three kids from 11 were to be guarding the flag itself. It was foolproof. They were the blue team, if you were going by the plumes in their helmets.

Meanwhile, the red team had set up their own battle plan. Thy were just as confident in it as the blue team was. The conch shell was blown and the battle started.

Thalia and Percy charged over the boundary line, yelling battle cries. The red team met them halfway, battling them with everything they had. Well, not everything. You couldn't kill or maim anybody in this game so...

As the game went on, it got more intense. Swings got more desperate, shields were brought out more often. Both teams were tiring out fast and were giving their all, but neither were gaining any traction. The fight had to end, and quick!

Suddenly, Percy felt a tug in his gut as he summoned the water from the creek to distract his opponents. He used that advantage to run over the boundary line, Thalia and his troops not far behind. They reached the perimeter and sprinted towards the exposed flag, glinting red in the dying sunlight. They slashed with the flats of their blades, swung with their hilts. Percy found an opening and grabbed at the flag, grasping it in his outstretched hand. He stopped in his tracks and tuned tail, his troops making a line for his escape. He had just sprinted the last few yards when he felt a sudden shift, like as if he stood up too fast. He was still able to cross the boundary line, though, capturing the win for his team.

Suddenly, a blood curling scream ripped through the air, silencing everyone and everything. Percy's blood ran cold. What had happened?

Then, a girl was visible coming through the door edge of the forest. Her black clothes were tattered and her face was scratched and dirty. Percy walked towards her, curious as to what made her scream. Suddenly, a snarl ripped trough the air as a hellhound leapt out through the trees, tackling the girl to the ground. She yelled in surprise as the furry beast smothered her.

Without thinking, Percy sprinted towards the fallen girl, picking up a discarded spear as he ran. He capped his sword and took aim with the spear. He threw the spear with all his might at the hellhound, hoping to kill it before it killed the girl. The spear met its mark, sinking deeply into the damned flesh of the hellhound. The hellhound fell sideways off the girl but then exploded in yellow sulfur-smelling dust. The girl coughed and sat up, brushing the dust from her hair. Percy finally reached her and helped her to her feet.

"Are you alright?" he asked, looking at the newfound demigod in interest. She looked right back. The girl had sea green eyes much like his own and her hair was jet black and shoulder length in multiple layers. Her skin tone was fair and she was only slightly shorter that Percy, about the same height as Annabeth.

"Yeah, I think so. Thanks for saving me." she said, her voice smooth and thankful.

"It's no problem. What's your name?" he asked.

"Oh, I'm Mera. Mera Servator." Mera said, extending her hand.

"Percy Jackson." Percy said, shaking her hand. He noticed her subtle wince and he looked to her leg, which was bandaged up pretty badly.

"You should really get that looked at. Come on, I'll get you a medic." Percy said, helping her limp over to Chiron, who was waiting by the creek. Mera's eyes widened as she saw him.

"Is that a centaur?" she whispered to him quietly. "I thought they were just myths. Okay, this is definitely a hallucination from the blood loss. Definitely." She kept on mumbling until they reached the waiting centaur, who had a first aid kit in his hand. He made her lay down and offered her a flask of nectar. She took it and sniffed it. She raised her eyebrow at Percy.

"Just drink it, it'll make you feel better." he said, trying to reassure her. She nodded and took a tentative drink but immediately recoiled from it.

"Why does this taste like my mom's chocolate chip cookies? That makes no sense." she said, oblivious to her already healing wound. She didn't notice the water from the creek float over and encase her leg, healing it. Percy and Chiron stared at the water in shock, as was everyone else. Percy raised his hands in defense.

"I'm not doing it." he said. Mera looked confused.

"What are you talking about?" she asked. Percy pointed to her leg and she screamed. The water immediately dropped back into the river. She looked even more shaky than before.

Suddenly, a glowing blue trident appeared above her head, revolving slowly in midair. Percy and everyone else stared at it. His gaze slowly lowered to Mera, who was looking more confused by the second. He had a sister.


	2. not an update

**NOTICE!**

* * *

Okay, I know that you might not want to see this, since this isn't an update, but I wanted to let you know that updates will be slower because when I type on my phone, the format gets all screwed up on desktop and on mobile. So, I will need to continue my updates from my computer, which isn't as portable as my phone. So I know that some of you may be mad. Trust me, I'm mad too. But I'm probably going to update faster because I am now on summer vacation. I'm also on a different softball team so practice is only once a week, but three hours long. (why...) Anyway, my weekends probably won't consist of a lot of updates because I have practices on Saturdays and at least three games per day on Sundays.

 ** _Fanfiction Information:_**

Identity Crisis: Don't worry. I will be updating this soon. The latest chapter is in the works. If you have any questions, please don't hesitate to PM me or to leave a review. I'll try to type faster.

A Different Identity:This is going to be continued. The next chapter is being worked on and will be posted as soon as it's ready.

Justice League Alternative: I've kind of lost interest in this story but it will be continued. I have a couple more chapters planned out and I will try to update them as fast as possible.

Wanted: I'm totally still interested in this story. There is no danger whatsoever about it being discontinued so stay tuned for a new chapter soon.

 _ **The Sea's Daughter:**_ This was meant to be a one-shot, but if you guys want another chapter, I'm sure that I can find the inspiration to give you guys a couple more chapters.

 _ **-** **Nightingale0708**_


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